Hello everyone! I've been planning on making a futuristic mod set in a dystopian world for a few years now. I've already figured out a lot of things, story wise. But now, I finally want to do some modding, and I'm stumped. I don't know which modding tool to use! I know, I'm greedy and everything, but I really need a powerful toolset that isn't too hard to use, and has good support. So, I've listed a few, and I could really use your opinion. If you think there are other and better toolsets, feel free to list them. Thank you.

Fallout 3 (GECK) -- open world and big support
Deus Ex (UnrealED) -- the game is already futuristic and dystopian, but also pretty old
Neverwinter Nights (Aurora) -- easy to use and good support
Witcher 2 (REDkit) -- newly released, but it is supposedly good and easy to use, however not very good support yet. Opinion on this toolset would be appreciated!

The mod is supposed to be story-driven, with loads of characters, quests, equipment and locations. You will control multiple characters in the story. The story will be focused on dark themes such as slavery, prostitution, conspiracies, drugs, treachery etc.